As a color filter, one having picture elements of red, green, blue, etc. formed on a glass substrate by a dyeing method, a printing method, an electro deposition method, a pigment dispersion method or the like, is used. A color filter by a dyeing method is produced in such a manner that an image is formed by a photosensitive resin prepared by mixing a dichromate as a photosensitive material to gelatin or polyvinyl alcohol, followed by dyeing. To form multi colors on the same substrate, reserve printing steps are required, whereby there is a problem that the process tends to be complex. Further, since dyes are used, it is poor in light resistance. The dichromate used as a photosensitive material is problematic also from the viewpoint of prevention of pollution.
A color filter by a printing method is prepared by transferring a heat-curable or photo-curable ink onto a glass substrate by such a method as screen printing or flexographic printing. The process is simple without necessity of dyeing or forming an image. However, a highly fine image can not thereby be obtained, and there is a problem in flatness of the ink.
A color filter by an electro deposition method is prepared by immersing a glass substrate provided with electrodes, in a bath containing a pigment or dye, whereby a color phase is deposited on the substrate by electrophoresis. It is excellent in flatness, but it is difficult to form a complicated pattern, since it is necessary to provide electrodes to the glass substrate beforehand.
In the pigment dispersion method, an image is formed by a colored resist having a pigment dispersed in a photo-curable resin. It has a merit such as high heat resistance or no necessity of dyeing, and it is capable of forming a highly precise image. Accordingly, this method is currently the most popular method for producing color filters. However, a colored resist having a pigment dispersed in a high concentration, is used, whereby the photo curability is poor, and the sensitivity is low, and further, there is a serious problem in the operation efficiency, since the chemical resistance is also low.
In the pigment dispersion method, image formation is carried out by a colored resist having a pigment dispersed in a high concentration. Accordingly, strong light absorption takes place by the pigment, and cure-inhibition by oxygen takes place, whereby the sensitivity used to be low. Accordingly, in order to form an image, a long period of exposure time is required, whereby the operation efficiency is very poor, and in order to prevent the cure-inhibition by oxygen, it is necessary to further form a protecting film to shield oxygen on the resist film, which makes the process further complex. Further, the image formed in such a manner is not sufficiently photo-cured, whereby the image is poor in the heat resistance and chemical resistance, and it has been necessary to protect the colored image at the time of forming a polyimide film which serves as an orientation film for liquid crystal.
An object of the present invention is to solve the above-mentioned problems of the conventional colored resists and to provide a polymerizable composition for a color filter having a high sensitivity and being excellent in chemical resistance.
Another object of the present invention is to provide a color filter of a high quality by using such a polymerizable composition.
The present inventors have strenuously proceeded with a research for the above objects and as a result, have found that a polymerizable composition for a color filter comprising, as an organic polymer material, a (meth)acrylate copolymer containing alicyclic (meth)acryloyl groups in its side chains, is highly sensitive, provides a high resolution and is excellent also in chemical resistance and pigment-dispersibility. The present invention has been accomplished on the basis of this discovery. In the present specification, "(meth)acryl . . . " and "(meth)acryloyl . . . " mean "acryl . . . or methacryl . . . " and "acryloyl . . . or methacryloyl . . . ". For example, "(meth)acrylic acid" means "acrylic acid or methacrylic acid".